Recently, pneumatic tires for automobiles have been required to have a wide range of performance properties, such as fuel economy (the performance in terms of rolling resistance), grip performance (handling stability) and abrasion resistance. Various methods have been proposed to achieve improvement in these performance properties.
For example, a known method for improving the abrasion resistance is to use natural rubber or butadiene rubber as a rubber component. This method, however, tends to deteriorate the grip performance. An exemplary method for enhancing both the abrasion resistance and grip performance is to increase the amount of a reinforcing agent such as carbon black and silica. In this method, however, the performance in terms of rolling resistance tends to be deteriorated.
Other methods for improving the abrasion resistance and grip performance include a method of adding a polymer obtained by polymerization of only an aromatic vinyl monomer, and a method of adding a hydrogenation product of a low-molecular weight aromatic vinyl-conjugated diene copolymer (Patent Documents 1 and 2). However, there still remains a demand to improve the grip performance and abrasion resistance as well as the performance in terms of rolling resistance in a balanced manner because these properties usually conflict with each other and it is difficult to improve these simultaneously.    Patent Document 1: JP-A 2007-112994    Patent Document 2: JP-A 2005-225946